1. Field of the Invention
The present invention relates to a technology for calculating a head-gap between a head and a disk of a storage device.
2. Description of the Related Art
Generally, a storage device such as a magnetic disk device or a magneto-optical disk device used to store data on a disk includes a head arranged in a contactless manner with respect to the disk. The head reads data from or writes data to the disk. While reading the data, the head senses magnetic signals or signals of laser beams reflected from the disk. Hence, the more the head is arranged proximal to the disk, the better is the sensitivity of the head to sense such signals, which improves the quality of retrieved data. In recent years, following the improvement in recording density of the disk, the distance between the head and the disk, i.e., the head-gap has reduced to, e.g., 10 nanometers.
Consequently, it has become increasingly necessary to monitor and regulate changes in the head-gap that may be affected by various surrounding conditions. In that regard, Japanese Patent Application Laid-Open No. 2004-14092 discloses a conventional technology for calculating and regulating the head-gap. According to the conventional technology, data required for calculating a head-gap is stored in advance in a disk. The head-gap is calculated based on the amplitude of a fundamental wave component and of a second frequency component of the data.
However, in the conventional technology, it is necessary to allocate a certain amount of storage area on the disk to store the data for head-gap calculation, resulting in less storage area for storing user data. Particularly, in recent years, the requirement is to manufacture disks with large storage capacity and high recording density. From this viewpoint, it is disadvantageous that the data for head-gap calculation occupies a certain amount of storage area on the disk.
Moreover, the head-gap can be calculated only at a predetermined interval at which the data for head-gap calculation stored in the disk is regenerated. In other words, the head-gap cannot be calculated at the time of, e.g., storing or regenerating signals of servo data. Hence, it is not possible to have real-time control on the head-gap.